1. Technical Field
This invention relates to a molded closure and the molding assembly for making the closure. More particularly, this invention relates to a molded closure having an auxiliary thread for removing incomplete injection runs that occur during the fabrication of such molded closures.
2. Description of the Related Art
The manufacture of molded polymeric closures is well known in the art. Injection molding techniques wherein a polymeric material is introduced into a molding assembly in order to form a molded closure are well known. Such molded polymeric closures often include substantially hollow cylindrical wall portions having smooth inner walls. A faulty run, or short shot, of the fabrication process sometimes results in the formation of a fragmentary closure containing no principal thread. Such a fragmentary closure is difficult to remove from the molding cavity due to the lack of engagable structure which may be used to pry the incomplete closure from the cavity. Therefore, the production of such a fragmentary closure often requires suspension of the process while non-process tools are used to pry the closure out of the molding cavity, thereby resulting in loss of production and increase in the likelihood of damage to the manufacturing equipment.
Current solutions to the problem of removing fragmented articles from a mold include molding structure into the polymeric article that must be engaged by a separate tool in order to remove the article. For example, U.S. Pat. No. 2,313,031 discloses a plastic container having a plurality of lugs molded therein. Upon the occurrence of a faulty run, the plunger of the molding assembly must be removed so that a separate tool may be introduced into the mold. The tool engages the lugs and then removes the article from the mold. However, none of the prior solutions provide a simple structure formed in the article that allows for the removal thereof from the mold cavity simply by removing the mold core.
Therefore, a molded closure formed with a core-and-cavity molding assembly is needed that includes a simple structure therein which provides engagement between the closure and the molding core, so that a fragmentary unit of such a closure may be removed from the molding cavity using only the engagement between the closure structure and the molding core.
It is an object of the present invention to provide a molded polymeric closure having a simple structure that facilitates the removal of an incomplete closure from the molding assembly.
It is another object of the present invention to provide a molding assembly for making molding closures that forms simple structure in all closures molded therein which facilitates the removal of an incomplete closure from the molding assembly.
It is a further object of the present invention to provide an auxiliary thread on an inner surface of a cylindrical molded closure that facilitates the removal of an incomplete form of such a closure from the molding assembly.
It is yet another object of the present invention to provide a tiered closure having at least one auxiliary thread therein to provide engagement between a fragmentary tiered closure and a tiered mold core.
It is still a further object of the present invention to provide a method for making a molded closure having a simple structure that facilitates removal of an incomplete unit from the molding cavity.
More particularly, the present invention is directed to a molded closure having a top wall and a side wall depending downwardly therefrom with both a first closure thread and at least one second closure thread disposed on an inner wall of said side wall, the first closure thread being an auxiliary thread which is directed inwardly from the side wall. The auxiliary thread is preferably disposed at or near a top end of the side wall, which may be closed. The second closure thread or principal thread of the molded closure part serves as a fastening means between the closure and either a container or another closure part. The principal thread is disposed toward the bottom open end of the closure. The principal thread is also preferably disposed on an inner wall of the side wall of the closure. The closure may include one or more principal threads in combination with an auxiliary thread. Furthermore, the molded closure may include one or more tiers in the side wall. The auxiliary thread and the principal thread may be disposed on the same tier or upon different tiers. However, in each embodiment, the auxiliary thread is disposed on the side wall of the closure at a location opposite to the location of the principal thread.
During the molding process, the auxiliary thread, like the principal thread, provides an engagement between the closure and the molding core. However, unlike the principal thread, the auxiliary thread is formed at or near the first end of the closure where there would otherwise be only smooth and/or non-threaded surfaces. Therefore, when an incomplete or fragmentary closure is formed having no complete second end containing the principal thread, the auxiliary thread is available therein to provide a means for removing the incomplete closure from the molding cavity using only the engagement between the auxiliary thread and the molding core. Thus, even when the principal threads of a closure have not been properly formed, a means is provided by the present invention to threadably remove ill-formed closures from the molding cavity without resort to non-process tools or suspension of the manufacturing process.
The auxiliary thread""s functionality is more limited than that of the principal thread. Namely, the auxiliary thread""s only function is to assist in the removal of closures, even incomplete or ill-formed closures, from the closure cavity by the engagement of the auxiliary thread with the molding core. However, the principal thread not only functions to engage the molding core during the removal of the closure from the molding cavity, but it also provides a fastening and/or sealing means between the closure and a container or another closure part. The auxiliary thread may be either identical to or structurally different from one or more of the principal threads of the closure. Indeed, there maybe incongruity between the auxiliary thread and the principal thread, wherein, for example, the depth, pitch, circumference, size, diameter or other aspect of the two threads differ. The auxiliary thread may be smaller in size than the principal thread, since the only required function of the auxiliary thread is to provide sufficient engagement between a fragmented closure and the molding core. The auxiliary thread does not require the depth necessary for the principal thread to properly function, so the auxiliary thread""s depth may be less than that of the principal thread. The pitch of the auxiliary thread may differ from that of the principal thread, since the principal thread must serve as a fastening and/or sealing means for the closure.
The apparatus for forming a molded closure having the auxiliary thread is also provided. The apparatus includes a molding assembly having a molding cavity and a molding core. The molding core includes a first inwardly projecting core thread in an outer surface thereof, preferably disposed toward the first end of the core, as well as a second inwardly projecting core thread. The second inwardly projecting core thread may have structural characteristics similar to those discussed above which differ from those of the first core thread, such as size, depth and pitch. When polymeric material is provided into the molding void between the molding cavity and molding core, the first core thread of the molding core forms an auxiliary thread on the molded closure formed therein.
It will become apparent that other objects and advantages of the present invention will be obvious to those skilled in the art upon reading the detailed description of the preferred embodiment set forth hereinafter.